1. Field of the Invention
The present invention relates to an antimicrobial topical solution comprising complexes of chitosan-silver, and in particular to solutions comprising complexed chitosan-silver bio-films, and to the methods of making the same.
2. Description of the Relevant Art
Topical antimicrobial solutions, or simply antimicrobial solutions, are widely used in today's society. Some uses are prophylactic, such as when a hand sanitizer is used prior to consuming a meal. Other times, users use a topical antimicrobial solution after encountering germs and microbes and prior to resuming to normal activities, such as immediately after using the bathroom and before returning to work. The latter scenario hopefully is routine for restaurant personnel. Healthcare acquired infections cause approximately to 103,000 deaths annually. This number of deaths is more than the combined total resulting from AIDS, breast cancer and automobile accidents. The economic burden is over $5.2 billion. It is the 4th leading cause of death. Inadequate hand hygiene also contributes to food-related illnesses, such as salmonella and E coli infection. According to The Center for Disease Control and Prevention (hereafter, the “CDC”), as many as 76 million Americans contract a food-borne illness each year. Of these, about 5,000 die as a result of their illness. Others experience the annoying symptoms of nausea, vomiting and diarrhea. The CDC lists hand hygiene as the number one preventive measure against the spread of healthcare acquired infections. The CDC came out with hand hygiene guidelines to better address the problem in October, 2002. The CDC made a strong recommendation for the use of hand sanitizers even when hands are not visibly soiled. Since the CDC guidelines were published, hand sanitizer sales in the United States have enjoyed double-digit growth, according to marketing information company A.C. Nielsen. Through December 2006, more than $70 million in all brands of hand sanitizers have been sold in U.S. supermarkets and drugstores, up 14.4 percent from the year before. The largest sales growth in recent years came in 2005, when more than $67.3 million in sanitizers were sold, a whopping 53.5 percent increase from 2004, according to A.C. Nielsen figures. The total annual U.S. infection prevention industry is $9.4 billion. Antimicrobial solutions can be applied in many forms. For example, many soaps contain antimicrobial agents that are used in combination with other soap ingredients. Hand sanitizers often come in forms of sprays, gels, lotions, ointments and other forms that a user rubs on his or her hands to kill present bacteria. The use of alcohol or quaternary ammonium chloride compounds is common in these types of solutions. Yet, the affects of these chemicals diminish greatly shortly after application. These current hand sanitizers are either flammable or, as in some cases, are showing less than effective results against more stubborn bacterial strains. Antimicrobial agents can also be applied with a wipe, such as a moist disposable towel. Some disposable towels utilize bleach or other chemicals that can have harsh and unintended consequences on a user's skin. Silver is naturally present in our environment, including the air we breathe, the water we drink and the foods we consume. However, silver does not occur naturally in the tissues of humans and animals. Silver is of extremely low toxicity to animals and humans. It is however, extremely toxic to simpler forms of life such as bacteria.
The antibacterial properties of silver have been known or suspected for thousands of years. The ancient Greeks used silver pots and other utensils. Hippocrates, the father of modern medicine, wrote that silver had beneficial healing and anti-disease properties. The Phoenicians stored water, wine and vinegar in silver bottles to prevent spoiling. In the early 1900s, it was not uncommon for people to place silver dollars in milk bottles to prolong the freshness of the milk. The malleability and non-toxicity of silver make it a useful material used in dental alloys for fittings and fillings. The widespread use of silver went out of fashion as an antimicrobial solution with the development of modern antibiotics. Many antibiotic drugs can be used to kill pathogens, but overuse has led to increased bacteria resistance to many of the antibiotics. Hence, there has recently been renewed interest in silver as a broad spectrum antimicrobial. Silver, when applied topically, continually demonstrates efficacy against microorganisms which have otherwise exhibited resistance characteristics. There are products on the market to treat or kill bacteria. These products are in a variety of forms, including liquid, foam, gel, lotion and ointment. Some of these products are described in the following patents:
U.S. Pat. No. 4,847,049 to Yamamoto is titled Method of Forming Chelated Collagen Having Bactericidal Properties. This patent provides a method for protecting renatured collagen against bacterial and fungal attack. The method includes contacting the collagen with a silver ion containing solution at a pH range of 4.0 to 9.0 and exposing the silver-chelated collagen to ultraviolet radiation.
U.S. Pat. No. 6,756,059 to Rozell et al. is titled Topical Composition, TopicalComposition Precursor, and Methods for Manufacturing and Using. This patent discloses a topical composition precursor prepared by melt processing a hydrophobic polymer composition that includes repeating pyrrolidone/alkylene groups wherein the alkylene groups contain at least 10 carbon atoms, and a hydrophobic polymer composition including repeating carboxylic groups and/or hydroxyl groups.
U.S. Pat. No. 6,716,895 to Terry is titled Polymer Compositions Containing Colloids of Silver Salts. This patent teaches how to provide varying release kinetics for the active ions in the compositions due to different water solubilities of the ions, allowing antimicrobial release tailored to a given application. The polymer compositions are stated to contain colloids comprised of salts of one or more oligodynamic metals such as silver.
U.S. Pat. No. 7,135,195 to Holladay et al. is titled Treatment of Humans with Colloidal Silver Composition. The composition includes water and silver particles, wherein the silver particles comprise an interior of elemental silver and an exterior of ionic silver oxide. The silver particles are described to be present in the water at a level of about 5-40 parts per million (Hereafter, “ppm”).
U.S. Pat. No. 6,881,424 to Kemp is titled Highly Acidic Metalated Organic Acid. This patent teaches how to mix a monovalent or polyvalent cation and an organic acid in the presence of a strong oxyacid. The resulting composition is described to be less corrosive to a ferrous metal than a solution of a mineral acid having the same acidic pH value, and is more biocidal than a mixture of the organic acid and a metal salt of the organic acid which mixture has the same acid normality value.
U.S. Pat. No. 5,895,782 to Overton et al. is titled Acid Replacement Solution for Cleaning of Non Ferrous Metals. This patent is taught to be used to clean non ferrous alloys such as copper, brass and high strength aluminum alloys. The solution is described to be prepared by mixing Ca(OH)2 and KOH with equivalent sulfuric acid in water, and then passing the solution through a 10 micron filter.
U.S. Pat. No. 6,383,095 to Newman et al. is titled Ionic Silver Complex. The invention is described to be made by combining ingredients water, a source of free silver ions, and a substantially non-toxic, substantially thiol-free, substantially water soluble complexing agent. This patent claims the use of an alkali metal and/or alkaline earth metal used as a counter-ion.
U.S. Pat. No. 6,583,176 to Arata is titled Aqueous Disinfectant. The aqueous solution is formulated by electrolytically generating silver ions in water in combination with a citric acid.
None of these patents describe the use of silver complexed with chitosan to form an antibacterial complex bio-film which allows for the silver complex to remain in contact with the surface of the skin and effectively kill bacteria for hours. It is an object of the present invention to provide an antimicrobial solution having high immediate or short term effectiveness. It is another object of the present invention to provide an antimicrobial solution having high residual effectiveness.
It is a further object of the present invention to provide an antimicrobial solution that readily bonds to a user's skin such that it remains in place.
It is a still further object of the present invention to provide an antimicrobial solution that is stable, portable and easily dispensable.
It is a still further object yet of the present invention to provide an antimicrobial solution that is gentle and that does not provide harsh consequences for a user's skin.
Thus there exists a need for an antimicrobial solution that solves these and other problems.